Circuit breaker with plug-in type terminal structure



July 25, 1967 F. L GELzHElsx-:R ETAL 3,333,078

CIRCUT BREAKER WITH PLUG-1N TYPE TERMINAL STRUCTURE Filed Oct. 13, 1965oFF FIG. l

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. wlTNEssEs United States Patent Gffice 3,333,078 Patented July 25, 19673,333,078 CIRCUIT BREAKER WITH PLUG-IN TYPE TERMINAL STRUCTURE FrancisL. Gelzheiser, Fairfield, and George F. Hawkes,

Jr., Trumbull, Conn., assignors to Westinghouse Electric Corporation,Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 13, 1965, Ser.No. 495,480 Claims. (Cl. 20G- 166) This invention relates to ci-rcuitbreakers of the type comprising a plug-in terminal structure, and moreparticularly to plug-in type terminal structures for use withmolded-case type circuit breakers.

For certain panelboard or load-center installations circuit breakers areconstructed with plug-in type line terminals that can be plugged ontobus-bar conducting stabs to electrically connect the circuit vbreakerswith bus bars. These plug-in type terminals or sockets are generallyresilient sheet-metal conductors that are mounted in the circuitbreakers in such a way that the bus bar stabs will engage spaced flatside surfaces of the conductors to force the side surfaces apart flexingthe generally resilient conductors .to provide contact pressure in themounted position. It is sometimes desirable to use an additional spring-means to bias t-he at side surfaces against the conducting stab. It isconsidered that this type of terminal structure does not always providethe most efficient and effective means for effecting contact pressure.

Accordingly, an object of this invention is to provide a circuit breakerwith an improved plug-in type terminal structure constructed to moreefficiently provide contact pressure in the mounted position.

Another object of this invention is to provide a circuit breaker with animproved plug-in type sheet metal terminal structure constructed forend-type contact with a conducting stab.

Another object of this invention is to provide an improved double-typecircuit breaker comprising two circuit-breaker mechanisms and animproved plug-in type terminal structure that .can be mounted onto acom-mon conducting stab to electrically connect the two mec-ha- `nismsto the conducting stab.

rBhe novel features that are considered characteristic of this inventionare set forth in particular in the appended claims. The invention, bothas to structure and operation, together with ladditional objects andadvantages thereof, will be best understood from the following detaileddescription when read in conjunction with the accompanying drawings.

In said drawings:

FIGURE l is a side sectional view taken generally alon-g the line I-I ofFIG. 2 with the plugin type ter-- minal structure Ibeing shown in sideelevation;

FIG. 2 is an end View, on a smaller scale relative to FIG. 1, of thedouble-type circuit breaker of FIG. 1 and part of a bus-bar stab;

FIG. 3 is a top plan view of the plug-in type terminal structure ofFIGS. l and 2;

FIG. 4 is a view taken along the line IV-IV of FIG. 3;

FIG. 5 is a view of the terminal structure of FIG. 4 taken along theline V-V of FIG. 4 with the bus-bar stab being shown in elevation; IandFIG. 6 is a front elevational view, with parts broken away, of theplug-in type terminal structure of FIGS. 3-5 with an additional springbiasing member connected to the terminal structure.

The general operation and certain parts of the circuit breaker disclosedherein are described more specically in the patent to Earl Bullis, Jr.Patent No. 3,200,217, issued Aug. 10, 1965.

Referring to FIG. 2 of the drawings, a double-type circuit breaker 9 isshown therein comprising an insulating lhousing that is composed of twomolded insulating parts, 11 land 13, forming two compartments. Each ofthe parts 11 and 13 comprises a back portion molded integral with foursides forming an open front. The open front of the part 11 is covered bythe back portion of the part 13 which serves as an insulating barrierbetween the two compartments, and the open front of the part 13 iscovered by a molded insulating cover 15. The three molded insulatingportions 11, 13 and 15 of the housing are held rigidly together by threerivets 18 (FIG. l).

The housing parts 11, 13 and 15 form two insulating compartments housingtwo circuit breaker mechanisms which are identical in construction andoperation, each of which mechanisms operates independently of the other.For this reason, only the mechanism enclosed by the housing part 11 willbe specifically described, it being understood that, unless otherwisementioned, the description applies to 'both of the mechanisms of thedoubletype circuit breaker.

The circuit-breaker mechanism, which is enclosed by the housing part 11and the back portion of the housing part 13, comprises a stationarycontact 21, la movable contact 23, a supporting metal frame 25, anoperatin-g mechanism 27 and a trip device 29.

The stationary contact 21 is welded, or otherwise rigidly secured, to laline terminal structure 31 that will be hereinafter more specificallydescribed. A stationary contact 33 (FIG. 3) for the circuit breakermechanism that is housed in the housing part 13 (FIG. 2) is also welded,or otherwise rigidly secured, to the line terminal structure 31.

The line terminal structure 31 is constructed to cooperate with a rigidload-center or panelboard conducting stab 35 in a manner to behereinafter more specifically described.

Referring to FIG. 1, the stationary contact 21 cooperates With themovable contact 23 that is welded or otherwise rigidly secured to agenerally C-shaped contact arm or switch arm 41. A bearing member 42 isprovided with a slot that is complementary with a slot in the upper partof the contact arm 41, and the bearing is provided with two upper legportions that iit into suitable slots in a molded insulating operatingmember 47. The bearing 42 transmits motion from the operating member 47to the movable contact Iarm 41 when the breaker is manually operated,and, as will be hereinafter explained, from the movable contact arm 41to the operating member 47 when the breaker is tripped automatically inresponse to an overload current condition.

The operating member 47 is a molded insulating member having an arcuatetrunnion `51 molded at each side thereof. The trunnions 51 fit androtatably ride on two arcuate surfaces 55 that are formed on themetallic supporting frame 25. The operating member 47 is supportedbetween the surfaces 55 of the frame 25 and the bearing 42 which issupported by the contact arm 41. The operating member 47 has a handlepart 59 molded integrally therewith, which handle part extends throughan opening 61 in the insulating housing to permit manual operation ofthe circuit breaker. Arcuate surfaces on opposite sides of the handle 59substantially close the opening 61 in all positions of the operatingmember 47.

The frame 25 supports an insulating pivot 65. A metallic trip member 79is pivotally supported at one end 77 thereof on the pivot 65. The otherend 82 of the trip member 79 is latched on a ledge in an opening in anarmature 85. The armature 85 is part of the trip device 29 which will behereinafter specifically described. The ends 77 and 82 of the tripmember 79 are offset and dis- The movable contact arm 41 is connected bymeansV of a liexible conductor 91 to the free end of a bimetal 93 thatis attached at its other end to a load terminal conductor 95. A loadterminal connecting screw 97, which is externally accessible, isprovided at the outer end of the conductor 95 to enable connection ofthe circuit breaker in an electric circuit. The load terminal conductor95 is welded or otherwise attached to a projection 99, extending outfrom the supporting frame 25. The terminal conductor 95 is givenadditional support by being looped over and welded to another projection101 extending out from the supporting frame 25.

The closed electric circuit through the circuit-breaker mechanismextends from the line terminal structure 31 through the stationary andmovable contacts 21, 23, the contact arm 41, the eXible conductor 91,the bimetal member 93, the load terminal conductor 95, to a conductingwire that would be electrically connected to the conductor 95 by meansof the screw 97 when the circuit breaker is in operating position. Sincethe movable contact arm 41 extends downward from its pivot, the arc isestablished adjacent the bottom of the housing in an arc chute 105, oneend of which is connected by a vent passage 107 to an opening in the endof `the housing beneath the load terminal screw 97.

The circuit breaker is manually operated to 'open and close the contacts21, 23 -by operation of the insulating handle `59. Movement of thehandle 59 clockwise from the full-line on position to the o position inwhich it is shown in dot-and-dash lines, carries the upper end of v thecontact arm 41 to the left of the line of action of the 'spring 87whereupon the spring acts to move the contact arm 41, with a snapaction, to the open position shown partially in dot-and-dash lines. Aprojection 109, molded integral with the housing part 11, acts as a stopto limit opening movement of the contact arm 41. Movement of theoperating handle 59 in a counterclockwise direction from the ott to theon position moves the upper end of the movable contact arm 41 to theright of the line of action of the spring 87 whereupon the springoperates to move the contact arm to the closed position seen in FIG. l.

The trip device 29 is provided to veiiect automatic opening of thecircuit breaker upon the occurrence of overload current conditions. Thetrip device 29 comprises the magnetic armature 85, the bimetal 93, aU-shaped magnetic member 111 that is secured to the bimetal 93 with thefree ends thereof facing in the direction of the magnetic armature 85and a spring 113. The upper end of the bimetal 93 is welded or otherwisesuitable secured to the Y terminal conductor 95 which is secured to theprojection 99 on the metal frame 25. The flexible conductor 91 is weldedor otherwise suitably secured to the lower or free end of the bimetal93, and it (the conductor 91) electrically connects the bimetal 93 withthe movable contact arm 41. The armature 85 is movably mounted on thebimetal 93 by means of the spring 113 that is secured at the lower endthereof to the bimetal 97 and at the upper 'end thereof to the armature85.

Upon the occurrence of an overload current below a predetermined value,the bimetal element 93 is heated, and when it is heated a predeterminedamount, it deilects, with a time delay, to the right as seen in FIG. lto eiect a thermal tripping operation. The armature 85, which issupported on the bimetal 93 by means of the spring 113,

is carried to the right with the bimetal to release the trip member 79.When the -trip member 79 is released, the spring 87 acts to rotate thetrip member clockwise about the pivot 65 to'a tripped position. Duringthis movement,

the line of action of the spring 87. moves to the right of lthe pivot 42of the contact arm 41 whereupon the spring biases the contact arm inanopening direction and moves the contact arm so Vthat the line of actionof the force exerted by the spring on the operating member 47 shiftsacross the pivot 51 whereupon the spring 87 actuates both the contactarm 41 and the operating member 47 to a tripped position. In order toprovide a visual indication that the -breaker has been automaticallytripped open, movement of the operating member 47 is stopped in animmediate position when a projection 117, molded integral with theoperating member 47, strikes the projection 89 that exetends from thetrip member 79. The circuit breaker is trip-free in that the breakerwill trip upon the occurrence of an overload even if the handle 59 isheld in the on or closed position.

Before the contacts can be closed following an automatic openingoperation, it is necessary to reset and relatch the mechanism. This isaccomplished by moving the operating handle 59 clockwise from theintermediate or tripped position to the full oli position. During thismovement, due to the vengagement of the projection 117 of the operatingmember 47 with the projection 89 of the trip member 79, the trip memberis moved counter clockwise about the pivot 65 until the latch end 82 isagain supported in the latched position on the armature 86. Thereafter,the circuit breaker can again be manually operated in the same mannerIhereinbefore described.

The circuit breaker is magnetically tripped automatically andinstantaneously in response to overload currents above the predeterminedvalue. Upon the ow of current through the bimetal 93, a magnetic flux,which is induced around the bimetal, takes the path of least reluctancethrough the magnet 111, across an air gap and through the armature 85.When an overload current above the predetermined value occurs, the pullof the magnetic flux is of such strength that the armature is attractedto the magnet 111 whereupon the spring 113 lluxes permitting thearmature to move,rre1 ative to the bimetal 93, to the right. Thismovement releases the trip member 79, and the contacts are opened in thesame manner hereinbefore described with respect to the thermal trippingoperation.

The line terminal 31 comprises a sheet-metal type generally resilientmember of conducting material. The member 31 is a at member havingoppositely disposed large- Vsurface-area at face surfaces andsmall-surface-area end surface means between the faces or face parts.'Ihe member 31 is formed as a generally U-shaped member (FIG. 4)comprising opposite leg parts 121 and 123 connected by means of a bightpart 125. The terminal member 31 is formed with a slot 127 (FIG. 5)therein, which slot extends Ythrough the lengthof the leg part 121 (FIG.4), through the bight part125, and downward a little more than half ofthe length of the leg part 123 (FIG .6). A projection 128 is bent-overfrom the leg part 123 to form a stop to position the terminal 31relative to the conducting stab 35.Y As was previously described, thetwo contacts 21 Yand 33 are Welded or otherwise suitably secured to oneof the sides or faces of the leg Ypart 123 of the terminal 31. Each ofthe contacts 21 and 33 cooperates with a different one of the stationarycontacts of the two circuit breaker mechanisms of the double-typecircuit breakerVY 9. The terminal 31 is mounted in the circuit breakerhousing 11, 13, 15 during assembly of the circuit breaker. During theassembly operation, the terminal 31 is moved into position when thecompartment of the circuitbreaker part 11 is open. The member 31 fitsover a projection 129 (FIG. l) that is molded as an integral part of thehousing part 11, and the leg 123 of the member 31 fits in a slot inanother projection 131 that is also molded as an integral part of thehousing part 11. A third projection 133 that is molded as an integralpart of the housing part 11 is provided to engage and position the shortleg 121 of the terminal 31. When the terminal 31 is in the position seenin FIG. 1, the housing part 13 (FIG. 2) is moved into position and thecover 15 is then moved to cover the open housing part 13. Thereafter,the parts are secured together by means of the rivets 18 (FIG. l). Theback wall of the housing part 13 has an opening in the lower back cornerthereof to permit positioning of the terminal 31 in the breaker housing.As can be seen in FIG. 2, the back corner at the line terminal end ofthe circuit breaker housing 11, 13, is provided with a slot or opening135 therein to receive the stab 35 when the circuit breaker is movedinto the mounted position.

When it is desired to mount the circuit breaker in a panelboard orload-center, the circuit breaker is moved into position to connect theterminal 31 with the conducting stab 35. During this movement, aconnecting part of the rigid at conducting stab 35 moves between twofacing end parts 139 and 141 (FIG. 5) of the end surface means of theterminal 31. The dimension between the facing end parts 139 and 141 isless than the thickness of the conducting stab 35 so that as theterminal 31 is forced onto the stab 35 the facing end surfaces 139, 141are biased apart spring charging the generally `resilient terminalmember 31 to provide contact pressure between the facing end surfaces139, 141, and the opposite sides of the stab 35. The member 31 isgenerally rigid with regard to forces applied in an endwise direction.Thus, it can be understood that as the member 31 is forced onto the stab35 the member 31 exes with a torsion or twisting action to provide atorsion-type or twisting-type spring bias of the facing end surfaces139, 141 against the conducting stab 35. This torsion action serves toprovide effective contact pressure between the facing end surfaces 139,141 and the conducting stab 35. As can be seen in FIG. 4, when theterminal 31 is moved into position on the stab 35 the projection or stopportion 128 on the member 31 serves to position the member 31 relativeto the stab 35.

If it is desired to further increase the contact pressure between thefacing end surfaces 139, 141 and the conducting stab 35 an additionalspring member 145 (FIG. 6) can be mounted on the terminal 31 to providean additional force biasing the facing end surfaces 139, 141 against thestab 35. As can be seen in FIG. 6, the spring 145 is a generallyU-shaped member with the end parts thereof mounted in suitable openingsin the bight part 125 of the terminal 31.

It is to be noted that the terminal member 31 is supported in thehousing 11, 13 and 15; but that the terminal does not cooperate with theinsulating housing in order to provide the biasing force for effectingcontact pressure between the facing end surfaces 139, 141 and the stab35 as would be the case, for example, if a spring member were positionedagainst part of the housing and the member 31 in order to providecontact pressure. Thus, if the insulating housing is distorted orrelieved to some extent because of heat that may be generated in thecircuit-breaker mechanism under excessive switching and short circuitconditions, this distortion of the insulating housing will not affectthe contact pressure between the terminal 31 and the stab 35.

For some applications, only one circuit-breaker mechanism may beutilized in only one compartment. In these cases, only one contact needbe welded to the contactsupporting leg 123.

While the invention has been disclosed in accordance with the provisionsof the patent statutes, it is to be understood that various changes inthe structural details and arrangement of parts may be made withoutdeparting from some of the essential features of the invention. It isdesired, therefore, that the language of 6 the appended claims be givenas reasonably broad an interpretation as is permitted by the prior art.

We claim `as our invention:

1. A circuit breaker comprising a pair of contacts operable to open andclose an electric circuit, a plug-in type terminal structure inelectrical series with said contacts, said plug-in type terminalstructure comprising a sheetmetal type member of generally resilientconducting material, said sheet-metal type member comprising oppositelydisposed flat face surfaces and end surface means between said at facesurfaces, said sheet-metal type member comprising facing end parts ofsaid end surface means which facing end parts are positioned to receivea conducting stab therebetween when said circuit breaker is plugged ontothe conducting stab, said plug-in type terminal structure constructed tocooperate with a conducting stab having a connecting part that has athickness greater than the dimension between said facing end partswhereby when said plug-in type terminal structure is forced onto saidconnecting part said facing end parts are forced apart with a torsionaction of said plug-in type terminal structure to spring charge saidplug-in type terminal structure to effect a bias of said facing endparts against said connecting part of said conducting stab.

2. A circuit breaker constructed in accordance with claim 1, whereinsaid sheet-metal type member comprises a one-piece member having a slottherein to form said facing end parts at opposite sides of said slot.

3. A circuit breaker constructed in accordance with claim 1, whereinsaid sheet-metal type member comprises an inverted generally U-shapedmember comprising a first leg and a second leg, said first leg formedwith a slot therein to form said facing end parts at opposite sides ofsaid slot, and means connecting said second leg in electrical serieswith said contacts.

4. A circuit breaker constructed in accordance with claim 3, wherein oneof said contacts is supported on a at face surface of said second leg.

5. A circuit breaker constructed in accordance with claim 1, whereinsaid sheet-metal type member comprises a member having a slot therein toform said facing end parts at opposite sides of said slot, and separatespring means engaging said member on opposite sides of said slot to biassaid facing end parts against said conducting stab.

6. Control apparatus comprising a circuit breaker, a conducting stabcomprising a connecting part having a thickness,

said circuit breaker comprising a pair of contacts operable to open andclose an electric circuit, a plug-in type terminal structure inelectrical series with said contacts, said plug-in type terminalstructure comprising a sheet-metal type member of generally resilientconducting material, said sheet-metal type member comprising oppositelydisposed at face surfaces and end surface means between said flat facesurfaces, said sheet-metal type member formed such that said end surfacemeans comprise facing end parts having a dimension therebetween that isless than said thickness of said connecting part of said conducting stabwhen said plug-in type terminal structure is not connected to saidconducting stab,

said circuit breaker removably connected to said conducting stab withsaid plug-in type terminal structure forced onto said connecting part ofsaid conducting stab, said facing end parts of said plug-in typeterminal structure positioned on opposite sides of said connecting partand forced apart by said connecting part to spring charge said plug-intype terminal structure to effect a bias of said facing end partsagainst said connecting part.

7. Control apparatus 4according to claim 6, said sheetmetal type membercomprising a one-piece member having a slot therein to form said facingend parts at opposite sides of said slot.

8. Control apparatus according to claim 6, said sheet-Y metal typemember comprising an inverted generally U shaped member comprising a rstleg and a second leg, said rst leg formed with a slot therein to formsaid facing end parts at opposite sides of said slot, and meansconnecting said second leg in electrical series with said contacts.

9. Control apparatus according to claim 8, one of said contactsSupported on a at face surface of said second leg.

10. Control -apparatus according to claim 6, said sheetmetal type membercomprising a member having a slot therein to form said facing end partsat opposite sides of said slot, and separate spring means engaging saidsheet metal type member on opposite sides of said slot to provide anadditional bias of said facing end parts against said connecting part ofsaid conducting stab.

References Cited UNITED STATES PATENTS Y Y 3,053,957 9/ 1962 Duield20D-166 3,111,354 11/1963 Hammerly et al 317-119 ROBERT K. SCHAEFER,Primary Examiner.

H. O. JONES, Assistant Examiner.

1. A CIRCUIT BREAKER COMPRISING A PAIR OF CONTACTS OPERABLE TO OPEN ANDCLOSE AN ELECTRIC CIRCUIT, A PLUG-IN TYPE TERMINALS STRUCTURE INELECTRICAL SERIES WITH SAID CONTACTS, SAID PLUG-IN TYPE TERMINALSTRUCTURE COMPRISING A SHEETMETAL TYPE MEMBER OF GENERALLY RESILIENTCONDUCTING MATERIAL, SAID SHEET-METAL TYPE MEMBER COMPRISING OPPOSITELYDISPOSED FLAT FACE SURFACES AND END SURFACE MEANS BETWEEN SAID FLAT FACESURFACES, SAID SHEET-METAL TYPE MEMBER COMPRISING FACING END PARTS OFSAID END SURFACE MEANS WHICH FACING END PARTS ARE POSITIONED TO RECEIVEA CONDUCTING STAB THEREBETWEEN WHEN SAID CIRCUIT BREAKER IS PLUGGER ONTOTHE CONDUCTING STAB, SAID PLUG-IN TYPE TERMINALS STRUC-